Molecular study on interaction mechanisms in supercritical water gasification of oily sludge model components

Oily sludge is the main byproduct generated during oil production, and its composition is quite complex. Consequently, it is challenging to elucidate the interaction mechanisms among various components in supercritical water gasification (SCWG). To address the aforementioned issue, n-dodecane (C₁₂H₂₆), 1-ethyl-2,2,6-trimethylcyclohexane (C₁₁H₂₂), styrene (C₈H₈), 1-ethoxybutane (C₆H₁₄O) and cyclopentene (C₅H₈) were selected as model components of oily sludge according to GC-MS analysis. The product distribution and interaction mechanisms between these components during SCWG were investigated via ReaxFF molecular dynamics (MD) simulation. The results show that the effect of temperature on model components is more pronounced in mixed SCWG when it is lower than 3250 K. Compared with pyrolysis at 2500 K, SCWG of C₁₂H₂₆ proceeds much faster due to the promoting effect of water, whereas no significant differences were observed in the SCWG of cyclic compounds. Last but not least, the synergy effect in mixed SCWG is mainly caused by the radicals produced by dissociation of water, not by the interactions between fragments produced by organics.